How do I reduce the boost on my 930?

[Emission]

(1986 930 - K-27 turbo - 1 Bar boost)

My car is pinging under full boost on the lousy 91 octane gas that California is forcing down our throats these days.

I want to return the boost to stock levels (.7-.8) where the car still runs smoothly.

Besides reducing the weight on my right foot to the gas pedal... I want to remove the 'upgrade' the previous owner did to the boost when he put the larger turbo in.

How is that done? My parts guy says there is a small 'black' spacer/gasket that needs to be removed. What is he talking about? Where is it located?

Thanks in advance.

[paulhagedorn]

From what I have read and not totally sure about, it is a wastegate shim. It causes the wastegate to dump at higher pressures, hence, you get more boost.

You should have less lag with less back pressure against the turbo, but obviously less boost means less power.

Have you considered trying to use octane booster?

[Emission]

That is the part! Where is the wastegate (I hope that is not a really stupid question)?

I tried mixing 4 gallons of racing fuel (100 octane) in 1/2 tank. It ran like a champ - not even a hint of pinging! Unfortunately, at $4.30 per gallon, my wallet (or my wife) cannot handle feeding the car like that.

I don't think the over-the-counter octane boosters will do enough. I have heard you can add straight 'Toluene' to the tank and increase octane quite a bit.... I am still a bit apprehensive with that.

I figure I will remove the 'shim' for daily drives, and put it back for the two weekends a year when the car will see the track (and run better fuel then).

[RJ Gilliam]

Could also be a simple spring. I would think that this previous owner put in a k27 he just put the simple 1bar boost spring in it.


Since you already have the k-27 it should spin up must faster than normal.

Do you get boost to come on before 3000?

Does this have the stock intercooler?

Does this have headers?

Unstock muffler?

[Emission]

The car is 100% stock except for the K-27 and the 1 bar of boost.

The boost comes on just past 3000 rpm with a heavy foot.

I don't know how he got the boost - he doesn't know (not a car guy), and his records don't show how either. I do know it will peg 1 bar pretty easily.

[RJ Gilliam]

I would bet its just the spring. If you want to know for sure there are 2 or 3 great Porsche people in So Cal. It depends on how mechanically inclinded you are feeling. The wastegate will have to come off. There is a spring that holds gate closed until the desired boost is reached then it opens. I dont know anything about a "shim" but I am no expert by no means. If you want it 100% stock, will be more than happy to trade you my stock turbo and wastegate for yours..(Yeah I know... keep dreaming)

Hope this helps.

Sounds like your car is a duplicate of mine..

[Emission]

Ha ha, I like the K-27... I just don't like the pinging.

Our cars are nearly identical (if the picture doesn't work, I will e-mail you one)!

[RJ Gilliam]

Looks like they only diff is the H4 headlights and I have a Euro exhaust.

Also try a little Octane boost could not hurt.

Dang that looks good. Hey I droppped you a PM with my email addy. Keep in touch.

Richard

[carmad]

I agree with the previous replies, unless you have an adjustable boost control, you need to replace the spring to stock.

[5axis]

Keep your K27 XXXX (there are many varients) and change the spring back to a stocker. Be carefull opening the wastegate, that spring is more forcefull than you expect. If the bolts are rust free, the job is quite simple and easy. Like most projects, it can go downhill from there. A cool thing to do while your there is add a straight pipe dump from the waste gate so when it lifts, it really sounds off. Mine does a great job of scaring off the ricers and vette guys.

david 89 turbo cab

[beepbeep]

Replacing stock spring to harder one on 930's is stupid ... car pinging on bad gasoline w/o possibility to lower the boost is exact type of problem that makes this a bad solution.

Higher boost can always be achieved by leaking pressure in hose that goes to the wastegate. It's much cheaper, wastegate doesn't need to come off and it can be made adjustable. All new turbocharged cars use this solution, most of them have magnet-valve that closes when boost reaches correct level.

Your wastegate sits under driver-side rear wheel-well. It's a big bell. Pins and bolts holding it to exhaust system are notorious for snapping off, so leave it to mechanic if you are "not a car guy".

When you swap to original spring, your boost will come down to 0.7 bar...you can always install boost controller to be able to adjust it further up.

Cheers!

[Emission]

Originally posted by 5axis
...add a straight pipe dump from the waste gate so when it lifts, it really sounds off.

How do I do that? Tell me more!

[Emission]

Originally posted by beepbeep
Replacing stock spring to harder one on 930's is stupid ... car pinging on bad gasoline w/o possibility to lower the boost is exact type of problem that makes this a bad solution.

When the prior owner did this, California was selling 92 octane gas (and you could even find 93 in places). As of a few months ago, California dropped to 91 octane. On 91 octane, the 3.3 liter is not happy under full boost.

I agree that it is not a 'safe' way to earn horsepower, especially if someone is running (or in danger of running) low octane gas.

Thanks for the pic! It will help.

[RJ Gilliam]

Here are some pics of a dump pipe.


Hope this helps

[Emission]

Originally posted by RJ Gilliam
Here are some pics of a dump pipe.


Hope this helps

That really helps.

It appears the 'stock pipe' has a small 'muffler' on it. Do they sell 'straight pipes' aftermarket, or do I have a muffler shop fabricate one? Other than noise, will anything else suffer (I would imagine not)?

[beepbeep]

I have just a short piece of pipe going out...no problems. you won't hear any difference until you reach full boost, and when you do there are other things to think about than noise :-)

Sounds terriffic! :-)

[RJ Gilliam]

Get the straight short piece sounds much better. Mine is just a stock Euro type. A straight dump pipe no muffler is on my list withthe K27 Turbo! Have fun

By the way Emission, your in SoCal, how come your not out doing Maibu Canyon today?

[Emission]

Originally posted by RJ Gilliam

By the way Emission, your in SoCal, how come your not out doing Maibu Canyon today?

I am home with a contractor "babysitting" him (don't trust him home alone) while he puts up crown molding in my kitchen/family room. While he is inside, I am outside washing/waxing/detailing the car.

I didn't know of any organized run on Mulholland today... I usually take the car out there on Sundays. Last weekend I went for a fun drive with a friend in his 993. Both cars are about the same speed - but both very different delivery.

[aseem]

Sorry for going off topic but, Richard I realy like your polished Fuchs. They are awsome. Did you do it yourself? What size are those rims?

[dean]

Here is some pics of the wastegate muffler that I made. Next time I would just use a straight pipe, but it might be too loud for me. Mine makes a nice howl on boost.

I just put the 1 bar spring in and I love it. But I must be stupid. :-)